For example, all the elements in group 1 are reactive metals, ... a pure substance contains only one element or compound. Mineral water is mostly water, but there are other substances mixed with it.

It is possible under certain conditions, for example in outer space, for helium and other noble gases to become part of compounds.A stable helium compound was created a few years ago, but only ...

Sodium and chlorine, two highly reactive elements, combine to form the stable compound sodium chloride (ordinary table salt). Questions for Discussion Describe the electron configuration of sodium.

For example, water isn’t on the periodic table because it is a compound, not an element. Water is made from the element hydrogen bonded to the element oxygen. Back to top ...